With the rapid development of display technique, the technique of the semiconductor elements as the core of a display apparatus has been developed rapidly. For the existing display apparatus, an Organic Light Emitting Diode(OLED), as a current-type light-emitting element, is increasingly applied to a field of a high performance display due to its features such as self-luminescence, rapid response, wide view angle, and the capability of being manufactured on a flexible substrate and the like. The OLEDs can be classified into two types, the Passive Matrix Driving OLED(PMOLED) and the Active Matrix Driving OLED(AMOLED). Since an AMOLED display has advantages such as low manufacturing cost, high response speed, power-saving, direct current driving applicable to a mobile device, a wide range of operating temperature, and the like, the AMOLED display is likely to replace the Liquid Crystal Display(LCD) to be a novel flat display of a next generation.
In an existing AMOLED display panel, each of OLEDs comprises a plurality of Thin Film Transistor(TFT) switching circuits. The TFT switching circuit manufactured on a glass substrate with a large size has non-uniformity on electrical parameters such as threshold voltage, mobility or the like due to limitation on production process, manufacturing level and the like, so that the current flowing through the AMOLED not only varies with the variation of the stress of the turn-on voltage generated when the TFT is in a ON state for a long time, but also varies with the drift of the threshold voltage of the TFT. As a result, the uniformity and the constancy on luminance of the display would be affected.
To address the above issues, as known by the inventor(s), in general, an AMOLED pixel compensation circuit would be adopted to compensate for the threshold voltage of TFT. Nevertheless, during the compensation phase, the sum of the data voltage and the threshold voltage(Vdata+Vth), or the sum of the power supply voltage and the threshold voltage(Vdd+Vth), would be written to the gate of the driving transistor. As a result, since the driving transistor is in a diode-connection state at this time, the internal resistance is large; thus, the larger the potential of the gate is, the slower the writing procedure is, and during the limited charging time, it is difficult for the potential Vdata+Vth or Vdd+Vth to be written exactly, thus resulting in a relative large difference between the data output from the Integrated Circuit(IC) and the data actually written to the pixel circuit, decreasing the display effect and quality of the display apparatus.